I have several back and forth on this.
I attempted paying for goods at a merchant store using my Union Bank card. Lo and behold, it declined but I was debited. Merchant advised i visit my bank.

Union advised I wait for seven working days for investigation. After the painful wait, I was told the transaction was successful. Merchant should liaise with his financial institution. Now, merchant says the fund is not in his account.

How do I resolve this bikonu.

No long story... The money is somewhere... Tell merchant to provide Statement of account for the past one month...
You also provide Statement of account for the past one month...
Simple

If you have experienced this, kindly share how it was resolved.

Here is the receipt from my bank saying transaction was successful. The copy from the POS says 'declined'.
Experienced bankers in the house, please help.

Here is the receipt from the bank.
Business section mods, kindly move to front page.

Here is the receipt from the bank.
Business section mods, kindly move to front page.
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Here is the receipt from the bank.
Business section mods, kindly move to front page